Method of forming masks for articles having intaglio designs



June 12, 1951 s. R. PRANCE 2,556,706

METHOD OF FORMING MASKS FOR ARTICLES HAVING ,INTAGLIO nsszcus Filed June 4, 1947 isI-iil I JNVENTOR.

(STANLEY ,ePEA/VOE BY i Patented June 12, 1951 METHOD OF FORMING MASKS FOR, AR-

TICLES HAVING INTAGLIO DESIGNS Stanley R. Prance, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application June 4, 1947, Serial No. 752,466

3 Claims.

- 1 This .invention relates to a method for formin high fidelity reproductions of uneven surfaces and is particularly concerned with a method for form- .ing paint masks and the like for use with indented .or raised surfaced designs.

It is an object of the invention to provide a method of reproduction of intaglio or cameo surfaces wherein high fidelity of the reproduced surface is obtained.

In carrying out the above object, it is a further object to use the reproduction or portions thereof as a masking means in the painting or other surface-finishing of the part reproduced.

Another object of the invention is to provide a method for forming high fidelity reproductions J ;of intaglio or cameo .surfaces wherein metallic evaporation is used to obtain the high fidelity reproduction, which vaporized metal is then used as a plating base whereby metal of any thickness may be built up thereon for adding strength to the structure.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

Fig. 1 is a plan view of a plastic horn button.

Fig. 2. is a view in section showing the horn button in place within an apparatus used for evaporating metal thereon.

Fig. 3 is a diagrammatic view showing the plating of metal onto vaporized metal within the horn button.

Fig. 4 is a view in section on an enlarged scale of a paint mask made from the surface reproduction.

Fig. 5 is a view in section on an enlarged scale of another paint mask made from the same surface reproduction whereby selected portions only of the horn button may be painted.

Fig. 6 is a view taken on line 66 of Fig. 1 showing the intaglio structure of the horn button design.

In the manufacture of horn buttons, emblems/ 2 tons, emblems, and the like having numerous colors thereon are made by this process wherein designs or trade-marks are molded into the plastic on the inner surface thereof in the form of an intaglio. This design is then selectively painted and presents an attractive appearance from the other side of the plastic article which has a smooth surface.

In the painting of these designs, it is necessary, as a rule, to use several diiferent masks whereby the design may be selectively colored as desired and wherein the mask or masks block out portions not to be painted. In view of the recessed or intaglio form of the design, the paint mask used must have high fidelity with respect to fitting into the design. This is important if clear-cut lines of demarcation between the various colors are to be obtained.

The manufacture of such a mask has in the past been a difiicult task and, in fact, so far as I am aware, no such masks have been made that are completely satisfactory with respect to fidelity and/or ease of manufacture.

My invention is directed to a method of making such a paint mask wherein the mask has the high fidelity necessary, due to the fact that the entire intaglio surface of the design is accurately and completely covered by means of metal to form a negative reproduction thereof.

Referring to the drawing, Fig. 1 shows a horn button, for example 20, having a design 22 in the central portion thereof. In carrying out my method, this horn button is placed on a block or support 24 within a vacuum chamber 26. Vacuum chamber 26 is in the space within bell jar 28. Also within the bell jar 28 is a filament 39 supported on electrodes 3| and 32, which filament is preferably made from tungsten, molybdenum or other satisfactory refractory metal. The electrodes 3! and 32 are connected to a suitable current source 34 which may be placed in circuit with the filament 30 through a switch 36. At the upper end of the bell jar 28, a take-off 38 is provided which connects to a vacuum pump (not shown).

The jar 28 seals around its lower peripheral lip 40 against a fiat surfaced table or support 42 to form a hermetic joint.

In the first step of the process, the plastic article 2 9 is placed with the surface to be coated facing the filament. The metal to be vaporized, such as gold, zinc, copper, nickel, silver, etc., is placed in the form of metal or a vaporizable metal salt either upon the filament 30 or in close proximity thereto as in a refractory boat 33, either suspended near the filaments or attached to the electrodes 31 and 32. The jar 28 is then evacuated to a very low pressure. I find that this pressure must be not more than 25 microns of mercury to be satisfactory. When the vacuum is at the desired figure, the switch 36 may be closed to cause the filament to become heated and vaporize the metal such as silver adjacent thereto. This evaporation of the silver causes a deposition thereof in a continuous phase all over everything within the bell jar and the silver completely coats the inner surface and all of the design indentations of the button 20. After coating, the vacuum may be released and the part removed from the jar.

In some cases, it may be desirable to clean the surface of the plastic article by a high voltage discharge within the vacuum chamber. This may be accomplished if desired, although in most instances, if the part is clean, it is not necessary.

In place of silver, any other suitable metal which will evaporate may be used, although silver, for purposes to be described hereinafter, is particularly desirable. Also, in place of metals, vaporizable metal salts may be used, which salts must be capable of depositing metal therefrom by evaporation, for example, nitrates, chlorides, etc., of desirable metals.

After the inner surface of the button 29 has been coated with metal, it is next placed as a cathode in a plating tank as shown in Fig. 3. A copper anode M is used if copper is to be plated thereon or any other metal anode in accordance with the plate desired. The electrolyte in the case of copper may be copper sulphate solution. This step is carried through under regular plating procedures and the copper is deposited in any desired thickness upon the thin coating of silver upon the plastic part. After a desired thickness is obtained, for example, in the order of a; to /8 of an inch, the plastic may be removed from the evaporated and plated material thereon either by dissolving of the plastic or by heating the plastic to a temperature sufiicient to permit stripping thereof from the negative reproduction.

In the manufacture of a paint mask from these 4 reproductions, it is obvious that several reproductions are necessarily made and are then cut apart as shown in Figs. 4 and 5 to form masks 46 and 43 respectively which, if placed together, would completely fill the design. The portions of the masks 46 and 48 are held together by wires 59 and 52 soldered or brazed to the various portions of the mask. Masks of this character have complete and high fidelity in connection with the design reproduced and will fit perfectly r into the intaglio surface of the design as shown in Fig. 6. In this manner, selected portions may be painted when using one mask and then by 'removal of this mask and replacement thereof when the article is placed beneath the filament. In this instance, the best position for the part to be coated may best be determined by trial.

In some cases, the plastic article may be masked before the vaporizing operation and in this manner only selected portions thereof receive the metal. Similarly, it may be desirable to selectively plate the vaporized metal by either masking out portions thereof and by completely removing portions prior to the plating operation. Any of these embodiments are fully comprehended as coming within the scope of my invention.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is asfollows:

1. The method of forming a mask for plastic articles having intaglio designs of appreciable depth thereon, the steps comprising, subjecting the article to a vacuum of not more than 25 microns pressure, vaporizing metal onto the intaglio design of the article by metal evaporation while maintaining said vacuum, removingthe metal coated article from the vacuum, and electroplating thereon another metal in a thickness sufficient to yield the desired strength, removing the reproduced surface from the surface of-the article on which it was deposited, and cutting away portions of the reproduced surface for forming a plurality of separate portions of the desired shape and then rigidly joining the desired portions of said article in spaced relation to one another whereby the completed mask has a, high fidelity of outline and shape for the intaglio design on the original surface.

2. The method as claimed in claim 1 which includes the added step of, masking out desired portions of the plastic article prior to the vaporizing step, whereby selected vaporization of the metal is obtained.

3. The method as claimed in claim 1 whichincludes the added Step of, masking out portions of the vaporized metal prior to the plating step, whereby selected plating of the vaporized metal is obtained.

STANLEY R. PRANCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 484,582 Edison Oct. 18, 1892 974,895 Leeds Nov. 8, 1910 1,892,755 Scheppmann Jan. 3, 1933 1,994,668 Russell Mar. 19, 1935 2,151,457 Williams Mar. 21, 1939 2,343,031 Spelker Feb. 29, 1944 2,394,930 McRae Feb.'12, 1946 OTHER REFERENCES Metal Industry, Sept. 1, 1936, Supplement on Electrometallurgy, pp. 239, 240 (an article by E. A. Ollard) 

